In DFT there is no \(\mathbf {O}(D,D)\) -symmetric completion of the Riemann curvature [1]}, [2]}, [3]}. Hence, the criterion of `\(\mathbf {O}(D,D)\) -symmetric curvature singularity' may appear unbalanced or somewhat unfair compared to GR.
With this in mind, we further analyse the geodesic deviation and the `tidal force' therein (again in string frame),
